User:Rebeca Rodriguez/Notebook/Chem 471/2015/09/16

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Objective

  • Remake 1mL gold nanofibers
  • Centrifuge gold nanofibers from last synthesis
  • Calibrate pH probes and create Tris and phosphate buffers

Au Nanofibers

  1. 10 new 1 mL fiber samples were prepared to replace the failed samples created on September 15th. Link to Michael's procedure here.
  2. Successful fibers were centrifuged at 12000 rpm, supernatant was removed, and left uncovered to allow the rest of the liquid to evaporate


pH Probes

  1. Probes were calibrated with stock solutions of 4.0, 7.0 and 10.0 pH calibration standards.

The following procedure is taken from Michael's notebook:

Buffer Solution Preparation

  • 500 mL 10 mM Tris buffer pH 9
  1. 0.60638 g (5.006 mmols)was placed in a 500 mL volumetric flask and was filled to the line with HPLC water
  2. The pH of the resulting solution was measured and was adjusted to pH 9 using 1 M HCl
  3. The pH and conductivity of the final solution was measured.
  • 500 mL 10 mM Phosphate Buffer pH 7
  1. The following phosphate buffer calculator was used to determine the necessary quantities of dibasic and monobasic sodium phosphate to use: http://serge.engi.tripod.com/MolBio/Buffer_cal.html
  2. From the website above, the following quantities were determined:
    1. 0.1967 g Dibasic sodium phosphate
    2. 0.53413 g monobasic sodium phosphate
  3. 0.1965 g dibasic sodium phosphate and 0.53410 g monobasic sodium phosphate was placed in a volumetric flask and the flask was filled to the line with HPLC water
  4. The pH and conductivity of the final buffer solutions were measured.


Note: It was determined after the preparation of the phosphate buffer that the wrong target pH had been entered into the phosphate buffer calculator. Rather than a pH of 7.0, a pH of 7.4 was entered into the calculator. This accounts for the flawed results of the phosphate buffer preparation.

Results

  • 500 mL 10 mM Tris buffer pH 9
    • pH after adjustment: 9.014
    • conductivity after adjustment: 111.8 μS/cm


  • 500 mL 10 mM Phosphate Buffer pH 7
    • Actual pH: 6.510
    • Conductivity: 1044.4 μS/cm

Due to time restrictions and the limited availability of the pH probes, it was impossible to correct the phosphate buffer.


Notes

Michael and I make a great team.

Matt Hartings :-)


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